While it is a bit of a restatement that has already been pointed out, perhaps its the other way around, has your client side been edited? perhaps your mpq no longer contains the display you're trying to use.
Granted, its much more likely that you're just using the wrong ID.
The same blue and white checkered box will always appear when you use an invalid display, for weapons, shields, just about anything. I recall live wow giving me that problem once... lol.